‘Rebound-saccade’ in the prism cover test

Abstract

If the fixing eye of a squinting patient is covered, a saccade to take up fixation follows which corresponds to the eccentricity of the image on the retina of the squinting eye. However, in some strabismus patients one finds a saccade even though the image on the retina of the squinting eye has already been deflected onto the fovea centralis with the aid of prisms. This saccade brings the eye into the primary position and displaces the image of the fixation target to a peripheral retinal point, so that the image must be recentred onto the fovea by a second saccade.

We propose to call this movement to and fro a ‘rebound-saccade’. This phenomenon indicates that, in patients with alternating strabismus, extraretinal information determined by the angle of squint influences rapid alternation of fixation between the right and left eyes. The rebound-saccade cannot be explained by anomalous retinal correspondence.